Swift 5.10 Release

What's Changed

• Escape CMAKE_Swift_FLAGS to preserve Windows path separators when running tests by @tristanlabelle in #435
• Tests: add vfs overlay for dipsatch by @compnerd in #437
• Disable Swift backtracer in a deliberately-crashing test. by @al45tair in #445
• Tests: add VFS overlay for Dispatch by @compnerd in #446
• build_script.py: use python3 by default by @MaxDesiatov in #449
• XCTestCase.fulfillment(…) missing on Linux #436 by @grynspan in #453
• Expectation handlers need to be @sendable. #454 by @grynspan in #455
• Add @mainactor to waitForExpectations(timeout:handler:) #428 by @grynspan in #452
• Bump the macOS deployment target to 10.13 in the Xcode project. by @grynspan in #459

Full Changelog: swift-5.9.2-RELEASE...swift-5.10-RELEASE